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Heavy-Duty Washer Dimensions (DIN 7989, M10 to M30)
Guide · Updated October 28, 2026
DIN 7989 covers thick (8 mm) flat washers for steel construction, bolt size M10 to M30. The standard has been replaced by DIN 7989-1 and DIN 7989-2, but the old name is still what most buyers search for. Every value below agrees across the fasteners.eu DIN 7989 table, the Aspen Fasteners DIN 7989 spec sheet and the Ferrobolt DIN 7989 table. Skipped: M33 and M36 (incomplete), the nominal hole sizes some catalogs use, and weights. Check your supplier for critical work.
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Step by step
- Pick the bolt size: Choose M10 to M30 to match the structural bolt.
- Read the hole: Inside diameter d1 sits between the min and max shown, giving clearance over the bolt.
- Read the outside diameter: Outside diameter d2 spreads the load over a wider area than a DIN 125 washer.
- Check thickness: All sizes are 8 mm thick (±1), much thicker than a normal flat washer.
- Allow for length: Add the 8 mm to your grip length when choosing bolt length.
- Order it: Designate as Washer DIN 7989 - 18 - St (hole size, material) or by bolt size per your supplier.
DIN 7989 washer dimensions (mm)
Columns: bolt size, inside diameter d1 min and max, outside diameter d2 min and max, and thickness s.
- Bolt | d1 min | d1 max | d2 min | d2 max | s
- M10 | 11 | 11.43 | 19.16 | 20 | 8 ±1
- M12 | 13.5 | 13.93 | 23.16 | 24 | 8 ±1
- M16 | 17.5 | 17.93 | 29.16 | 30 | 8 ±1
- M20 | 22 | 22.52 | 36 | 37 | 8 ±1
- M24 | 26 | 26.52 | 43 | 44 | 8 ±1
- M27 | 30 | 30.52 | 49 | 50 | 8 ±1
- M30 | 33 | 33.62 | 54.8 | 56 | 8 ±1
Worked example: M20 structural bolt
An M20 DIN 7989 washer has a 22 to 22.52 mm hole, 36 to 37 mm outside and is 8 mm thick. With a washer under the head and the nut, add 16 mm to the steel stack when sizing the bolt.
Common problems
- Bolt too short: forgot the 8 mm washer thickness in the grip length.
- Washer sinks into slotted hole: use a plate washer or larger outside diameter.
- Mixing with DIN 125: thin washers will dish under structural preload.
FAQ
What is a DIN 7989 washer?
A thick (8 mm) flat washer for steel construction, used under bolts and nuts where a larger, stiffer bearing surface is needed, often to fill out slotted or oversized holes.
DIN 7989 vs DIN 125?
DIN 125 is a thin general-purpose washer. DIN 7989 is 8 mm thick with a larger outside diameter for structural joints.
Why does one catalog show 14 mm and 18 mm holes?
Some catalogs list nominal or Form B (finished) sizes such as 14 / 24 mm for M12 and 18 / 30 mm for M16. The min / max values shown here are the ones three sources agree on.
Why stop at M30?
M33 and M36 appear in only one table without complete min values, so we left them out.
What material?
Usually steel 100 to 250 HV, also stainless A2 and A4. Weights are left out because sources differ.
Related guides and calculators
- Thick washers (DIN 7349)
- Small series washers (ISO 7092 / DIN 433)
- Chamfered washers (DIN 125 B / ISO 7090)
- Spring lock washers (DIN 127 B)
- Serrated lock washers (DIN 6798)
- Large OD washers (DIN 9021)
- HV structural nuts (DIN 6915)
- HV structural bolts (DIN 6914)
- HV structural washers (DIN 6916 / ISO 7416)
- Square washers for timber (DIN 436)
- Square taper washers (DIN 434 / 435)
- Flat washer size chart (SAE, USS, metric)
- Clamping washer dimensions (DIN 6340)
- Hex nut with collar dimensions (DIN 6331)
- T-slot bolt dimensions (DIN 787)
- T-slot stud dimensions (DIN 6379)
- All free machinist calculators
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